Selective signaling system



June 20, 1933. J. LESH 1,914,376

. SELECTIVE SIGNALING SYSTEM Filed Oct. 2, 1930 Ely;

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fig 3 --InuEn cu" Laurence J. Lash Patented June 2th 1933 siyn n ea ing his .li i i ILA a.

LAURENCE J. 111581111, OF

CHICAGO, ILLINQIS, ASSIGNGB, BY BIL'ESIIE ASSIGNLKIENTS, TO

rron or DELAWARE SELECTIVE SIGNAIJJSTG SYSTEM Application filed October 2, 1930.

. he present invention relates in general to selective signaling systems and more particularly to such systems employing tuned vibrating reeds in the generation and filtration of the signaling; currents.

One object of the invention is the provision of an improved and simplified method of tuning the vibrating reed. l-lerctofore, it has been the practice to change the tuning of a. reed by shifting its position in its support, either increasing or decreasing its length, or by shifting the position of a weight fastened to the vibrating portion of the reed. According to a particular feature of the present invent-ion, the reed may be quickly and easily adjusted to vibrate at a desired frequency without interrupting its motion.

According to another feature of the invention, the tuning of a vibrating reed is accom plished by changing the direction or intensity of the magnetic flux in which the reed is vibrating.

Another feature of the invention concerns the method of varying the magnetic flux in which the reed is vibrating, which may be done either mechanically or electrically.

Other features of the invention will become apparent from the following detailed specification when read in connection with the accompanying drawing.

In the drawing. Fig. 1 shows, by means of the usual schematic diagram, a signaling system employing the present invention. Fig. 2 is a perspective drawing of one arrange ment for adjusting the frequency of a tuned vibrating reed according to the present in.

vcntion.

1 shows the invention applied to a selective signaling ortelegraph system and dis closes the method of changing the frequency of a tuned vibrating reed by electrically the magnetic field in which the reed is vibrating. The oscillator shown as O is similar to the tuned reed osci lator disclosed and claimed in m (lo-pending application, Serial No. 353,283, filedApril 8, 1929. The frerpienry meter M, shown in the right-hand portion of 1 in diagrammatic form, is of the type shown and illustrated on page 9 of Cir ular llo. 166i--A entitled In licat- Serial No. 485,947.

ing instruments for direct and alternating currents, published by the lVestinghouse Electric and Manufacturing (30., East Pittsburgh, Pennsylvania. The meter has been modified by the addition of contacts .21 and 22 which are adapted to be engaged by the pointer 20.

Referring in detail to Fig. 1 of the drawing, when the circuit of battery 10 is closed to the filament of tube 1, the oscillator 0 will oscillate at a frequency dependent upon the normal period of vibration of the tuned reed 13. The operation of the oscillator is explained in detail in my above-mentioned pending application and only a brief description of the same need be given here. As soon as the filament circuit of tube 1 is closed a plate current flows from the plate of tube 1, the driving magnet 2, primary winding of transformer 1 to the positive pole of the plate battery 11. The magnet 2 attracts the tuned reed 13 and the movement of the reed brings about a decrease in the magnetic field of the polarized magnet 3, thereby inducing a potential in the coil of this magnet which is impressed upon the grid of tube 1. The induced potential is in such a direction as to make the grid of the tube more negative with respect to the filament, thereby decreasing the flow of current in the plate circuit of the tube and allowing the tuned reed 13 to retract in the opposite direction. The movement of the reed 13 to the left increases the magnetic flux through the coil of magnet 3, thereby inducing a potential in the Winding which is of opposite polarity, and makes the grid of tube 1 more positive with respect to the filament, thereby again increasing the plate current through the magnet 2. This operation continues and the 0scillator O continues to oscillate at a frequency equal to the normal period of vibration of thetuned reed 13. The pulsating current in the plate circuit of the tube passes through the primary winding of transformer 14 and induces an alternating current in the second ary winding which is connected directly to theout going line.

The incoming line at the receiving end is connected to the filament and grid of an amplifying tube 15. The potential on the grid of tube 15 varies in accordance with the alternating current transmitted over the line. rtccordingly the plate current through the primary winding of transformer 18 is of this same frequency. The secondary winding of coils A. The pointer 20 is attached to the movable coils B and C. The resistors R1 and R2 and the reactors X1 and X2 are provided to adjust the meter to a particular normal frequency. In'the present case the resistors and reactors are so chosen that with the normal frequency of oscillator 0 being received at the meter, the pointer 20 will be in a position mid-way between contacts 21 and 22 and neither of these contacts will be closed. Any increase in the frequency of the current received by the meter will cause the pointer 20 to swing in a clockwise direction and close contacts 22. A decrease in the frequency of the received current will cause pointer 20 to move in a counter-clockwise direction and close contacts 21.

- It will now be assumed that the oscillator 0 is oscillating at its normal frequency and that pointer 20 of the frequency meter M is midway between contacts 21 and 22 and neither of these cont-acts are closed. When the key 7 is operated to the left, closing contact 9, a circuit is closed from the positive pole of battery 10, key 7 and its contact 9, magnet 4, to the negative pole of battery 10. The electromagnet 4 is energized and the magnetic field produced by this magnet increases the frequency of the oscillator by a definite amount, depending upon the strength of the current flowing through magnet 4 and the proximity of the magnet to the end of the reed 13.

The frequency at which a reed will vibrate, or the natural period of vibration of a tuned reed, is dependent upon the stiffness of the reed which is the restoring force that tends to keep it in its normal position. The stiffer the reed, the greater the restoring force and the higher the frequency of vibration. When the electromagnet 4; is energized the magnetic field set up by this magnet attracts the reed 13' and tends to keep it in its normal position. That is, with the reed in its left or right-hand position the magnet 4 attracts the reed and tends to 5 bring it back to normal. While the reed is up by the electromagnet 4c is to aid the restoring force or stiffness of the reed itself and the reed accordingly will vibrate at a higher frequency.

rom the foregoing it will be seen that the operation of key 7 to its left-hand position energizes the magnet 4 and causes the oscillator 0 to generate a pulsating current of a frequency somewhat higher than the normal oscillating frequency. A corresponding alternating current is transmitted over the line through transformer 14, is amplified by the tube 15 at the receiving end, and flows through the frequency meter M. The increase in frequency of the alternating current flowing through the frequency meter M brings about an unbalanced condition of the torques between the movable coils and the stationary field coils, and the movable coils of the meter are rotated to again bring about a balanced condition of the resulting torques. As the movable coils rotate in a clockwise direction, the pointer 20 which is attached to these coils also moves in a clockwise direction and closes contact 22. This completes a circuit for the buzzer 24 from ground on the pointer 20 to battery at the buzzer. The buzzer 24 may be ad justed to a certain definite pitch to indicate that an increase in frequency has taken place. The buzzer continues to operate as long as the key 7 at the sending end is in its lefthand operated position. As soon as the key 7 is returned to normal, magnet 4 is deenergized and the tuned reed again vibrates at its normal period of vibration. ing current now received by meter M is of normal frequency and allows the pointer 20 to again return to its position midway be tween contacts 21 and 22.

When the key 7 at the sending station is operated to its right-hand position to close contact 8, a circuit is completed for the electromagnets 5 and 6 in series with the battery 10. The effect of the magnetic field set up by the magnets 5 and 6 is the opposite of that previously described for the magnetic field set up by magnet 4. WVhen the reed 13 is attracted by the driving magnet 2 of the oscillator and starts its movement to the right, the magnet 5 tends to attract the reed The alt-ernat- 3 induced negative potential on the grid of tube 1, and the magnet 2 is deenergized, the

reed 13 restores to its normal position but the magnetic field of magnet 5 opposes the,

larly, when the reed 13 swings to the left 3' the magnetic field produced by magnet 6 aids the movement of the reed and tends to draw it still farther to the left. When the driving magnet 2 is again energized and the reed is drawn to the right, the magnet 6 tends to i slow up this operation and accordingly slows down the movement of the reed. From the foregoing it will be seen that the magnetic fields produced by magnets 5 and 6 are opposed to the restoring force of the reed 13 and therefore slow down the frequency of vibration of the reed.

With key 7 in its right-hand operated position the magnets 5 and 6 are energized and the frequency of oscillation of the oscillator is reduced a definite amount, depending upon the value of the current flowing through the magnets and 6 and the position of these magnets with respect to the reed. The resulting alternating current is sent out over the line, amplified by the tube 15, and flows through the frequency meter M. This current is of a lower frequency than the frequency for which the meter M is adjusted and brings about an unbalanced condition of the torques between the movable coils and the field coils of the meter. The movable coils and the pointer are rotated in a counter clockwise direction to again bring out a balanced condition of the meter and the pointer 20 closes its contacts 21, thereby completing a circuit for the buzzer L3. The buzzer 23 is adjusted to a different pitch than buzzer 2-1 to indicate the decrease in frequency of the received current. The buzzer is operated as long as key 7 at the sending station is in its right-hand operated position. When the key 7 is released, the normal frequency of the oscillator O is again sent out over the line and the meter M returns to its normal position opening the circuit of buzzer 23.

hen used in a telegraph system, the key 7 would be operated to its left-hand position in accordance with the dots of the telegraph signal, and to its right-hand position in a"- cord auce with the dashes of the s gnal. Each dot signal transmitted from key 7 would therefore increase the frequency of the alternating current sent over the line and cause the frequency meter M to complete the circuit for buzzer The dash of the telegraph signal would reduce the frequency of the oscillator O and at the receiving end would cause the frequency meter ill to complete the circuit to buzzer 23. Since the two buzzcjrs are adjusted to produce different tones, the telegraph message could be read directly from the operation of these two i buzzers. Instead of connecting the contacts 21 and 22 to buzzers as shown in the drawing, these contacts might be comiccte'l to the dot and dash magnets of a printing te g aph instrun'ient and the message rccoree-d on a recording tape.

F 2 of the drawing discloses an arrangement for ad ustin the tunin of a flblfi'tll'l reed b" mecnanicallv Shiitln? the 7OS1iZ1OIl of a permanent ma net with resoect to the reed. The apparatus comprises a base plate of wood or other suitable non magnetic material on which are mounted the magnets and reed of the oscillator and the permanent magnet for adjusting the tuning of the Tie tuned reed 56 is clamped to the mounting block by means of clamp 5?". The two magnets 51 and 52 of the oscillator are mounted on opposite sides of the tuned reed by means of mounting brackets 53 and 54. These magnets are mounted facin one an other with their pole faces a sufhcient distance apart to allow the tun-ed reed 56 to vibrate freely between the two magnets. 31 weight 58 is mounted on the tuned reed 56 and the position of this weight may be shift ed along the length of the reed to effect a broad tuning of the reed.

The permanent magnet 61 is suspended from an arm 59 which is held in an upright position by means of the mounting bracket 60. The magnet is held at its upper end between the two clamping plates 62 and 63 by means of clamping screws 65. he clamp- 63 is provided with two projections which pass on either side of the end of the arm 59, and a pin 64: is inserted through holes in these two projections and the end of arm 59, forming a pivot point about which the bar magnet 61 is free to rotate. The magnet 61 is clamped in such a position that its lower end is opposite the end of the tuned reed 56. A micrometer adjusting screw 66 is provided which extends through the arm 59 and whose end rests against the permanent magnet 61. A spring 67 attached to arm 59 and the mag net 61 holds the magnet in place against the end of the adjusting screw 66. When the adjusting screw is turned in a clockwise direction the end of magnet 61 is brought closer to the end of the tuned reed 56 and the frequency of the reed is increased since the effect of the magnetic field of the permanent magnet is to aid the restoring force or the stiffness of the reed itself as fully explained hereinbefore. hen the adjusting screw is turned in a counter-clockwise direction the spring 67 keeps the magnet 61 in contact with the end of the adjusting screw and the magnet 61 is drawn farther away from the end of the tuned reed 56, thereby reducing'the magnetic field in which the reed is vibrating and decreasing the frequency of the tuned reed. Thus it will be seen that the frequency of the oscillator, which is governed by the natural period of vibration of the tuned reed 56, maybe easily adjusted to a desired value by means of the adjusting screw 56 without stopping the motion of the reed.

Although the invention has been illustrated as applied to a tuned reed oscillator it is to be understood that the invention is not limited to the application shown, but may be used for frequency adjustment in various devices employing tuned reeds or tuning forks, such as'oscillators, filters, tuned reed relays,

etc. Various modifications may be made by those skilled in the art without departing from the spirit of the invention.

It will be understood, also that where a tuned reed is referred to in the claims, this expression is intended to include and cover a tuning fork or equivalent device.

Having described the invention, what is thought to be new and is desired to have protected by Letters Patent will be pointed out in the appended claims.

What is claimed is:

1. In combination, a tuned reed, a plurality of electro-magnets located in different positions with respect to said reed, means for causing said reed to vibrate at its normal frequency, and means for adjusting the frequency of said reed to a desired value either above or below normal by energizing a particular one or more of said electro-magnets.

2. In combination, a tuned reed, means for causing said reed to vibrate at its normal frequency, means for producing a magnetic field whose axis is parallel to the plane of said reed to increase the frequency thereof,

and means for producing a second magnetic field whose axis is at right angles to the plane of said reed to decrease the frequency thereof.

3. In combination, a tuned reed, means for causing said reed to vibrate at its normal frequency, two magnets located at right angles to each other in close proximity to said reed, means responsive to the energization of one of said magnets for causing said reed to vibrate at a frequency below normal, and means responsive to the energization of the other of said magnets for causing said reed to vibrate at a frequency above the normal frequency of said reed.

4. In combination, an oscillator having a tuned reed, means for causing said reed to vibrate at its normal frequency, a first mag net located opposite the end of said reed with its pole face at right angles to the plane of the reed, a second and a third magnet located on opposite sides of said reed with their pole faces parallel to the plane of the reed, means for energizing said first magnet to cause said reed to vibrate at a higher frequency, and means for energizing said second and said third magnets to cause said reed to vibrate at a lower frequency.

5. In a signaling system, a line, means for transmitting an alternating current of a particular normal frequency over said line, means for decreasing the frequency of the current by a definite amount, means for increasing the frequency of the current by a definite amount, and signals at the receiving end of said line selectively operated in accordance with the changes in frequency.

6. In a signaling system, a line, means for transmitting an alternating current of a particular normal frequency over said line,

means for decreasing the frequency of said current by a definite amount, means for increasing the frequency of said current by a definite amount, a plurality of signals at the distant end of said line, and means re sponsive to current of said normal frequency for maintaining said signals inoperative and responsive to changes in frequency for selec tively operating said signals.

7. In a signaling system, a line, means for transmitting an alternating current of a particular normal frequency over said line, means for decreasing the frequency of said current by a definite amount, means for increasing the frequency of said current by a definite amount, an indicating mechanism at the receiving end of said line having a normal position and two operated positions, and means responsive to current of said normal frequency for maintaining said mechanism in its normal position and responsive to the changes in frequency for selectively operating said mechanism to its operated positions.

8. In a signaling system, a sending and a receiving station, a tuned reed oscillator at the sending station for transmitting an alternating current to said receiving station at a frequency equal to the normal vibrating frequency of the tuned reed, a plurality of electro-magnets, means for energizing certain of said magnets to decrease the frequency of vibration of said reed, means for energizing other of said magnets to increase the frequency of vibration of said reed, and audible signals at the receiving station selectively operated responsive to the changes in frequency.

9. In a signaling system, a sending station and a receiving station, a tuned reed oscillator at said sending station for transmitting an alternating current to said receiving station at a frequency equal to the normal frequency of vibration of the tuned reed, a signaling key, means responsive to the operation of said key in one direction for increasing the frequency of vibration of said reed, means responsive to the operation of said key in the other direction for decreasing the frequency of vibration of said reed, a signal at the receiving station operated responsive to an increase in frequency, and a second signal at the receiving station operated responsive to a decrease in frequency.

10. In a signaling system, a sending and a receiving station connected by a line, means at the sending station for transmitting an alternating current of a particular frequency over said line, a signaling key, means re sponsive to the operation of said key in one direction for decreasing the frequency of said current to a predetermined value, means responsive to the operation of said key in the other direction for increasing the frequency of said current to a second predetermined value, and signaling means at said receiving station selectively responsive to the changes in frequency.

11. In a signaling system, a sending and a receiving station, a tuned reed oscillator at said sending station for transmitting an alternating current to said receiving station, means for producing a magnetic field whose axis is parallel to the plane of said reed to increase the frequency of vibration of said reed thereby increasing the frequency of the transmitted current, means for producing a magnetic field whose axis is at right angles to the plane of said reed to decrease the frequency of vibration of said reed thereby decreasing the frequency of the transmitted current, and signaling means at the receiving station selectively responsive to the changes in frequency.

12. In combination, a base, a thin, flat vibratory reed, a mounting support on said base, means for clamping one end of said reed to said support leaving the other end free to vibrate, means for producing sustained vibrations of said reed, an arm extending upward from said base, a bar magnet pivoted at its upper end to said arm with its lower pole opposite the free end of said reed, and micrometer adjusting means for regulating the distance between said pole of the magnet and the end of the reed to adjust the frequency of vibration of the reed.

13. In a signaling system, a line, an alternating-current generator, means for coupling said generator to said line to transmit an alternating current thereover, means for increasing and decreasing the frequency of the current output of said generator from its normal frequency while maintaining it coupled to said line, and signals at the receiving end of said line selectively operated in accordance with the changes in frequency.

In witness whereof, I hereunto subscribe my name this 29th day of September, A. D.

LAURENCE J. LESH. 

